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M. Kronstein, M.-A. Néouze:
"Photoluminescence Properties of Novel Ionic Silica Nanoparticle Networks";
Poster: 4^th EuCheMS Chemistry Congress, Prague, Czech Republic; 26.08.2012 - 30.08.2012; in: "4^th EuCheMS Chemistry Congress - Final Program", (2012), S. P-676.

Novel hybrid materials ionic silica nanoparticle networks (ISNN) were synthesized. The efficient formation of this novel hybrid material allowed to process the material into monolithic gels or transparent films. The ISNN presented very interesting photoluminescence properties.
For the synthesis of those hybrid materials, silica nanoparticles with an average diameter of 16 nm were modified with N-(3-propyltrimethoxysilane)imidazole. These imidazole modified silica nanoparticles reacted with halogen functionalized linkers. The coupling reaction, between the modified nanoparticles and the linker molecules, is a nucleophilic substitution. This substitution can be considered as a "clickchemistry-like" reaction. The molecules used as linkers consists in aromatic or condensed aromatic compounds containing two opposite-standing CH2Cl-groups, such as p-Dichloroxylene or 4,4'-Bis(chloromethyl)-1,1' biphenyl.
The photoluminescence measurements performed on the ISNN hybrid materials showed emission bands over a broad range in the visible region. The silica nanoparticles, as well as the imidazole or chloroalkyl modified silica nanoparticles are non luminescent. In the specific cases where the pure dichloro linkers were photoluminescent, their emission maximum occured at a different wavelength than for the corresponding hybrid material.
SAXS measurements (Small Angle X-Ray Scattering) indicated a short range order which was assumed of being the origin for the photoluminescence properties of these hybrid materials. The short range order in form of strong π-π stacking interactions in the hybrid material was investigated when observing emission wavelength shifts by changing the linker.
The measured quantum yields up to 80% making this ISNN extremely promising for photoluminescence applications.

Green chemistry; Ionic liquids; Luminescence; Silicates; Sol-Gel processes;

Projektleitung Marie-Alexandra Néouze:
Ionische Verknüpfung von Nanopartikeln